1. Field of the Invention
This invention relates to separation microcolumn assemblies for microgas chromatographs and the like.
2. Background Art
There are numerous challenging issues associated with the realization of a fast microGC (μGC) utilized as a “fieldable analytical instrument.” “Fieldable analytical chemistry” is defined as “the practice of producing appropriate qualitative and/or quantitative information with analytical instruments that are operated at or near the sample collection location and which convert data to chemical information in a time frame that is consistent with near real-time application.”
GC systems are chemical instruments by which the components of a gaseous mixture can be separated, identified, and the constituent concentrations qualified. FIG. 1 shows the schematic of a GC system in which a sample is vaporized and injected onto the head of the separation column 10, the heart of the system. The sample is transported through the column by the flow of an inert, gaseous mobile phase. The column itself is coated with a stationary phase that greatly influences the separation of the various gaseous species. The structure of the stationary phase affects the amount of time the compounds take to move through the column. That is, as various molecules pass through the column, the time spent adsorbed on the stationary phase (column wall) is a function of the gas type, stationary phase used, and temperature. As compounds emerge from the column, they pass over a detector 12. The compound and detector interact to generate a signal whose size corresponds to the amount of compound present in the sample. The signal can be recorded by a recorder 14. The delay of a sample in passing through the column identifies the species present.
Conventional GC systems tend to be large, fragile, and relatively expensive table-top instruments. MEMS technology promises the realization of a complete microGC system with much smaller size, reduced analysis time and greatly-increased portability compared to its traditional ancestors. Such systems should make gas chromatography a pervasive method for gas analysis, with applications in monitoring food freshness, industrial process control, and the environment. The prospect of a wristwatch-size microsystem capable of analyzing the air we breathe with part-per-billion sensitivity would have wide applicability in homeland security.
As mentioned above, the basic—and the heart—of a GC system is its separation column. There are numerous efforts around the world to miniaturize the separation column (along with the rest of the instrument) and reduce its power consumption, allowing rapid changes in the column temperature and decreasing the analysis time. Sandia National Laboratories has recently introduced a football-size “miniGC” that is considered the state-of-the-art today.
The following U.S. patent documents are related to the present invention: U.S. Pat. Nos. 6,527,835; 6,096,656; 6,527,890; 6,386,014; 6,270,641; 6,134,944; 6,068,780; 5,792,943; 5,583,281; 5,544,276; 4,881,410; 5,377,524; 5,989,445; 5,992,769; and 6,109,113.